Desmarestiales

{{Use dmy dates|date=October 2023}}

{{short description|Order of algae}}

{{Automatic taxobox

|image = Desmerestia aculeata.jpg

|image_caption = Desmarestia aculeata

|image_alt = Desmarestia aculeata

|taxon = Desmarestiales

|authority = Setchell & Gardner

|subdivision_ranks = Families

|subdivision =

• Arthrocladiaceae
• Desmarestiaceae

}}

Desmarestiales is an order in the brown algae (Phaeophyceae). Members of this order have terete or ligulate (flat) pinnately branched thalli attached by discoid holdfasts. They have a sporophytic thallus usually aggregated to form a pseudo-parenchyma.Pound F.E. 1962 “The Biology of the Algae” Edward Arnold Ltd. The order gets its name from the genus Desmarestia, which is named after the French zoologist Anselme Gaëtan Desmarest (1784–1838).Genaust, Helmut (1976). Etymologisches Wörterbuch der botanischen Pflanzennamen {{ISBN|3-7643-0755-2}}{{cite journal|last1=Lamouroux|first1=Jean Vincent Félix|author-link1=Jean Vincent Félix Lamouroux|title=Essai sur les genres de la famille des thalassiophytes non articulées|journal=Annales du Muséum d'Histoire Naturelle, Paris|date=1813|volume=20|pages=43–45|url=http://img.algaebase.org/pdf/562E29B40301733B85MQrj41D8EE/17071.pdf|access-date=11 December 2017|language=fr|oclc=2099267}}

As the general name of the class suggests, their pigmentation is brown.